Institution: | a Divisão de Biologia Celular, Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Caixa Postal 486, Cep 30 161-970, Belo Horizonte, MG, Brazil b Departamento de Bioquímica-Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Caixa Postal 486, Cep 30 161-970, Belo Horizonte, MG, Brazil c Fundação Ezequiel Dias, Rua Conde Pereira Carneiro, 80, Cep 30 510-010, Belo Horizonte, MG, Brazil |
Abstract: | The cDNAs (Tx3-2 and Pn3A) encoding precursor of toxin Tx3-2 and an isoform called Pn3A have been isolated from a library constructed from stimulated venom glands of the spider Phoneutria nigriventer. The cDNA of Tx3-2 reveals the presence of a signal peptide of 21 amino acids and of an intervening propeptide (with 16 amino acids) preceding the toxin sequence, which was followed by additional amino acid residues at the C-terminus (C-terminal peptide), implying post-translational modifications of the synthesised peptide. The deduced amino acid sequence for the mature toxin confirms the previous sequence published. In addition, by using the whole-cell patch clamp technique, we have determined that purified Tx3-2 decreases L-type currents present in GH3 cells. Finally, the presence of the cDNA Pn3A, with high sequence identity with Tx3-2, reveals the existence of a putative new toxin showing, at the cDNA level, 85.4% identity in its whole segment. |